Tex. Estates Code § 51.057

(a) Except as provided by Subsection (b), if a citation or notice is required to be served in a probate proceeding on a person who is now deceased but survived the decedent who is the subject of the proceeding, the citation or notice must be served on one of the following:

(1) the personal representative of the deceased person's estate, as provided by Section 51.056; or

(2) each distributee of the deceased person's estate, if:

(A) the personal representative has been discharged;

(B) the independent executor has filed a closing report or a notice of closing of the estate; or

(C) there is no administration of the estate ordered by a court, including if:

(i) the deceased person's will was admitted to probate as a muniment of title;

(ii) the court finds there is no necessity for administration in a judgment in a proceeding declaring heirship under Chapter 202; or

(iii) the court approves a small estate affidavit under Chapter 205.

(b) If there is no court order determining the distributees of the estate of the deceased person who survived the decedent or no personal representative of the deceased person's estate has been appointed, the citation or notice must be served on the unknown distributees of the estate by publication in the county in which the probate proceeding described by Subsection (a) is pending and, if known, the county of the last residence of the deceased person, if that residence was in a county other than the county in which the probate proceeding is pending.

(c) If service by publication is required by Subsection (b), the court may appoint an attorney ad litem to represent the interests of the distributees of the deceased person's estate, whether known or unknown.